This invention relates to improvements in IQF (individual quick freeze) freezers and more particularly to improvements in conveyor belts used in such freezers for the freezing of food such as peas, cut corn, berries, etc. The invention is herein illustratively described by reference to the presently preferred embodiment thereof; however, it will be recognized that certain modifications and changes with respect to details may be made without departing from the essential features involved.
Wire mesh type conveyor belts composed of successively linked transverse wire helices are commonly employed in food freezers as a means to support the food particles in transit through the freezer while permitting air fluidization of the particles during the process. The mesh openings are sufficiently small to support articles like shelled peas and, given the strength of stainless steel and certain other metals, the wire diameter can be small so as to present a low resistance to upward flow of fluidizing freezing air through the belt and through the food particles spread over the surface area of the belt. Persons working in this art and designing such systems heretofore have consistently specified belts of this type. The theory was that airflow resistance through the mesh should be as small as possible compatible with particle support and belt strength requirements so as to maximize the effectiveness of airflow in fluidizing and quickly freezing the mass.
In accordance with this invention, however, it has been discovered that the previously desired low resistance to flow of air through such belts is detrimental to the overall process, particularly the economics thereof in commercial installations. With the uniformly low airflow resistivity of the belt mesh itself, inevitable variations in depth or permeability of the mass of particles over the area of the belt cause material differences in the volumetric airflow through regions of the massed particles over the area of the belt and thereby cause material differences in the freezing and fluidizing effects achieved. In consequence, in order to assure proper freezing of all particles, it is necessary to limit the speed of travel of the conveyor through the freezer to meet the requirements of the particle mass where it is thickest or least readily penetrated by the airflow. This not only slows down production, but it also has a tendency to vary product uniformity from the standpoint of IQF specifications, including uniformity of surface glaze and uniformity of temperature gradients achieved within the individual food particles.
In accordance with an object of this invention, the advantages of wire mesh conveyor belts, of conventional construction or otherwise, either in existing systems or in newly constructed systems, may still be employed, but without the limitations mentioned above.
A further object of this invention is to devise a means to improve the production rate capability and the uniformity of processing capability of food particle IQF freezers using wire mesh type conveyor belts. A related object is to achieve these results in a manner also improving the mechanical and wear characteristics of the conveyor belt.
A further advantage of the invention lies in its relatively simple and inexpensive implementation both in existing and in new freezer mesh type conveyor belts.